The observed internal plateau of X-ray emission in some short gamma-ray bursts ( GRBs ) suggests the formation of a remnant supramassive magnetar following a double neutron star ( NS ) merger .
In this paper , we assume that the rotational energy is lost mainly via gravitational-wave ( GW ) radiation instead of magnetic dipole ( MD ) radiation , and present further constraints on the NS nuclear equation of state ( EoS ) via mass quadrupole deformation and r -mode fluid oscillations of the magnetar .
We present two short GRBs with measured redshifts , 101219A and 160821B , whose X-ray light curves exhibit an internal plateau .
This suggests that a supramassive NS may survive as the central engine .
By considering 12 NS EoSs , within the mass quadrupole deformation scenario we find that the GM1 , DD2 , and DDME2 models give an M _ { p } band falling within the 2 \sigma region of the proto-magnetar mass distribution for \varepsilon = 0.01 .
This is consistent with the constraints from the MD radiation dominated model of rotational energy loss .
However , for an r -mode fluid oscillation model with \alpha = 0.1 the data suggest that the NS EOS is close to the Shen and APR models , which is obviously different from the MD radiation dominated and mass quadrupole deformation cases .